Effects of Separate and Mixed Grinding on the Rate of NiO-MoO₃ Binary Solid State Reaction

Abstract

Reactants of NiO-MoO₃ binary solid state reaction are preliminary ground either separately or together in air (dry) or in cyclohexane (wet) by a laboratory vibro-mill. Subsequently, the rate of nickel molybdate formation on heating at 600°C in air was determined by applying Dander rate equation. Dry grinding of NiO followed by an intimate mixing with MoO₃ and by wet co-grinding brought the highest rate, due to the large amounts of lattice imperfections introduced into NiO. Preliminary grinding of MoO₃, on the other hand, was effectiveless, because of high degree of agglomeration which hinders the intimate mixing on subsequent wet vibromilling. Dry co-grinding was also effective, although less amounts of lattice im-perfections are introduced, compared with dry separate grinding, presumably because of originating precursory products at the contact points of foreign reactant particles during grinding.